1. Field
The present invention relates to semiconductor light-emitting elements.
2. Description of the Related Art
The flip-chip mounting is a mounting method in which light is mainly extracted from a substrate side opposite to an electrode surface of a semiconductor light-emitting element. This mounting is also called face-down mounting. The structure of a semiconductor light-emitting element used in the face-down mounting includes both a p-pad electrode and an n-pad electrode on a surface opposite to an element substrate. The electrode surface is mounted on an external substrate. A metal bump is used for the face-down mounting, or an alloy is used as an adhesion layer. For example, JP2009-164423A discloses a semiconductor light-emitting element in which a bump is used to electrically connect the chip surface (electrode surface) and the external substrate. JP2009-164423A is described as follows: a transparent conductive film is stacked on a nitride semiconductor layer (p-type semiconductor layer); through holes are created in the transparent conductive film; a metal electrode layer at the outermost surface is extended in the through holes; this causes a contact member, which is part of the metal electrode layer, to directly contact the nitride semiconductor layer; and a strength of adhesion is thus increased.
The semiconductor light-emitting element disclosed in JP2009-164423A has a large distance (step) between the surface position of a p-pad electrode formed on the p-type semiconductor layer and the surface position of an n-pad electrode formed on an n-type semiconductor layer exposed by removing part of the p-type semiconductor layer. Thus, in order to bond the semiconductor light-emitting element to a sub-mount substrate and to make them level, it is necessary to adjust the height of an n-side bump and the height of a p-side bump.
Recently, various semiconductor light-emitting elements have been disclosed. They include, via an insulation film over a p-type semiconductor layer, an n-pad electrode electrically connected to an n-type semiconductor layer. They also include both a p-pad electrode and the n-pad electrode over the p-type semiconductor layer for their structural arrangement. The semiconductor light-emitting elements having such a structure can avoid the problem regarding a step between the p-pad electrode and the n-pad electrode, thereby improving characteristics of the face-down mounting. In addition, a contact region between the p- and n-pad electrodes and the mounting surface is made large. This also makes it possible to improve contact strength, precision, and heat dissipation characteristics.